Mount for co-witnessing sighting devices for firearms having sheet metal receiver covers

ABSTRACT

A sight mount for firearms having short sight mount blocks and having sheet metal receiver covers. A mount base is pivotally connected with the sight mount block and has a sight support platform that is positioned above the receiver cover and provides support for an optical sighting device. A lock member has releasable locking engagement with the lock retainer members and having a portion thereof engaging the rear sight block and securing said mount base against movement from said sighting position. A rear sight member is defined by an upturned portion of the lock member and has a sighting notch that is visible in co-witnessing relation when viewing through the optical sighting device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to tactical firearms that are utilized by tactical and special operations personnel for military and law enforcement activities. More particularly, the present invention concerns a firearm sight mount system providing a for co-witnessing metal and optical sighting devices. Even more specifically the present invention concerns sight mount devices that provide for co-witnessing of metal and optical sighting devices on firearms having minimal length or space for mounting sighting devices due to the presence of thin, typically stamped metal receiver covers and other receiver components to which sight mounts cannot be secured for serviceable use.

2. Description of the Prior Art

Millions of reasonably light-weight and inexpensive tactical firearms have been manufactured in various countries and have been in wide use throughout the world by military and law enforcement personnel. Examples of these inexpensive tactical firearms include the Avtomat Kalashnikova Model 1947, widely known as the AK-47, which was developed by a Russian Army Sergeant, Michail Kalishnikov, and placed in service during 1947. This particular firearm has been widely used by the military and law enforcement services of many other countries. Another example of an inexpensive, widely used tactical firearm is known as the AK 100. Tactical firearms of many other manufacturers are similar in that the firearm has a relatively short or compact forward receiver or sight block section, which is a machined component, on which a rear sighting device, typically a pivotal metal leaf sight, also known as an adjustable “iron sight” is mounted. The receiver of these types of firearms has a receiver cover that is composed of stamped sheet metal and thus lessens the weight and also the cost of the firearm. Being composed of sheet metal, the receiver cover cannot be drilled and tapped and thus cannot provide efficient and durable support for attachment of any other type of sight mount device that might be desired.

Of late, it has been deemed desirable to provide tactical firearms and firearms of general character with various types of sighting devices, including co-witnessing sighting devices. Typical sighting devices for this type of firearm is a metal rear sight, also referred to as an “iron sight”. The rear iron sight typically has a sighting notch with which a blade or post front sight mounted near the muzzle of the barrel is aligned. A co-witnessing sighting device is typically typically employs an optical sighting device, such as an electronic reflex sight, such as the precision electronic red dot sighting devices that are sold under the trade designation “Comp M2” and “Comp M3” by Aimpoint, AB, Jagershillgatan 15, SE-213 75, Malmo, Sweden. These electronic optical sighting devices display a precision red dot that is visible to the user of the firearm during sighting. For precision aiming of the firearm the red dot is positioned on the target. When the position of the red dot of the optical sighting device is properly adjusted relative to the optical lens the bullet being fired by the firearm will strike on or very near the apparent location of the red dot in relation to the target. Thus, with the red dot of the optical device appearing as if it were on the target the user will fire a bullet and it will strike the intended spot on the target, subject of course to conventional variables such as wind, distance to the target and the inherent accuracy of the rifled bore of the barrel. A conventional sighting system employing a post or blade front sight and a mechanical rear sight defining a rear sighting notch is employed in conjunction with the optical sighting device. When viewing through the optical sighting device, the conventional mechanical sighting system is visible, thus establishing the co-witnessing relationship of the two sighing systems. The user of the firearm can visualize either or both of the sighting systems as desired.

The rear metal sight is often provided in the form of a pivotally mounted sight device, a part of which is typically moveable to adjust the sighting mechanism for elevation and part of which is fixed to the receiver or rear sighting device of the firearm. Another popular rear sight form is an elongated sight, also known as a sight leaf that is pivotally supported for sight adjustment movement. The elongated sight leaf is marked with range identifying indicia and a leaf slide member providing a sighting slot is capable of being positioned at any desired location along the length of the elongated sight leaf. The leaf slide member typically engages one or more tapered ramps that establish elevation control for the rear portion of the sighting slot for purposes of elevation control to compensate for the trajectory of the bullet as it travels from the muzzle of the firearm barrel to the target. For lateral sight control, to compensate for windage, the leaf slide member can be provided with an adjustment mechanism for lateral movement of the rear sighting slot or the front sight of the firearm may be laterally adjustable for windage.

Co-witnessing of the metal and optical sighting devices occurs when the front sight of the firearm is visible when the user of the firearm is aiming the firearm by looking through the optical sight. And when an electronic red dot type sighting marker is being used, the front sight of the firearm and the red dot of the reflex type optical sight each indicate the striking position of the bullet on the target. This enables the user of the firearm to employ both the metal front sight of the firearm and the red dot of the electronic reflex optical sight simultaneously or alternatively. While red dot optical devices are widely used for reflex type sighting devices, dots of any other suitable color may be used as well. Thus, the present invention is not intended to be limited by or restricted to the use of red dot sighting indicators.

Since many of the inexpensive tactical firearm models, such as the AK-47, have small exposed receiver sections known as rear sight blocks for rear sight mounting, typically only the factory supplied metal rear sights can be employed. The sight mount seats of the receivers are sufficiently small that they can accommodate only the typical rear leaf sight assembly. Only due to the development of the present invention has it become possible to also mount an electronic reflex optical sighting device in co-witnessing relation with a metal rear sight mechanism, providing a sighting capability that has heretofore been considered unavailable for the AK-47 and other similar inexpensive tactical firearms.

Recognizing the need for co-witnessing sights on standard AK-47/AKM/AK-74/AK-100 series rifles, attempts have been made to attach mounts to the rifle structure. Though side mounts and side rails have been developed for such purpose the results have been deemed ineffective. Applicant has developed a modern optic mount for Mikhail Kalashnikov's famed Avtomat rifle, also known as the AK-47. Unfortunately the standard AK-47/AKM/AK-74/AK-100 series of rifle does not lend itself to this particular endeavor. This is simply due to the minimal length of the rear sight block and the presence of a removable stamped sheet metal top receiver cover extending rearwardly from the rear sight block. The top receiver cover protects the receiver structure from contamination, but it is composed of thin sheet metal and lacks sufficient structural integrity to provide support for any kind of sight mount attachment. The Russian arms development system encountered this same issue when it attempted to mate early night vision devices with the basic rifle design. The Russian solution was to mount a universal optics rail onto the left side of the rifle's receiver. This short side rail allowed a day/night optic to be easily mounted/removed though side mounting of the optics has been found cumbersome and the optics is easily damaged during use of the weapon in field conditions.

During the design phase applicant's intention intention was to develop a simple yet rugged mount which could be easily attached in the field, without requiring any modification of the rear sight block of the rifle. The optical sight needed to be low enough to co-witness with the factory iron sights. Additionally the optical sight needed to mount a simple electronic red dot sight to improve the hit probability of the rifle at commonly encountered engagement distances. In addition, the co-witnessing sight mount and sight installation needed to be affordable, bearing in mind the low manufacturing cost of AK 47 type rifles.

It was discovered that using the mounting structure for the factory rear iron sight as an attachment point a sighting system could employ a mechanical rear sight system and an optical sight system. By doing so a very lightweight and simple mount can be employed which is low enough to have a co-witnessing relation with a replacement rear sight. In addition, the pivotally mounted sight can be pivoted upwardly to allow the top-cover of the rifle to be removed for routine maintenance.

The sight mount of the present invention is of simple design and construction and adds significantly to the usefulness of AK-47 and similar rifles that are acquired under field conditions. The dual co-witnessing sight mount simply replaces the conventional rear sight without requiring any modification of the rear sight mounting system of the rifle. The mount body is machined from steel and features a hardened steel rear sight blade/leaf-spring. The sight base of the mount seats snugly down in the channel designed for the stock rear sight, allowing clearance between the base and the receiver cover. Mounted onto a cantilevered plate of the base is a Burris FastFire Micro Red Dot Sight. This features a 4 MOA dot with automatic brightness control via a forward-facing sensor. The sight is Parallax free at 50 yards and is recoil-resistant to 1000 Gs. The lens is multi-coated and it is powered by a common CR 2032 lithium battery. To better manage battery life, the sight has an On/Off switch mounted on the side. Operating temperature of the sight is −10 to 130 degrees F. To protect the sight from impacts, an aluminum shroud covers the top. The shroud has cutouts for access to the ballistic adjustments and the on/off switch. The finish of the sight mount is a matte black and the total weight of the mount and optic is under 3.5 ounces. With the optic mounted the iron sights co-witness in the lower one third of the field of view. This allows the user to accomplish an instant transition to the iron sights in the event the electronic optic should fail.

SUMMARY OF THE INVENTION

It is a primary feature of the present invention to provide a novel sight mounting mechanism for tactical firearms having short or small receivers with insufficient mount seat space for mounting metal and optical sighting devices, that simply and efficiently adapts the standard AK-47 and related firearms with the capability for co-witnessing metal and optical sights.

It is another feature of the present invention to provide a novel co-witnessing sight mounting mechanism for tactical firearms, having a leaf-spring sighting member that is releasably mounted to a one-piece sight mount base and serves both as a metal sighting member and for minimizing or retarding free pivotal movement of the one-piece sight mount base.

It is also a feature of the present invention to provide a novel co-witnessing sight mounting mechanism for tactical firearms having magnet members that attract a rear portion of the one-piece sight mount base to the conventional rear sight block of an AK-47 type tactical firearm and thus ensure that the co-witnessing sighting mechanism is properly positioned for accurate aiming of the firearm for each ammunition round that is fired.

It is an even further feature of the present invention to provide a novel co-witnessing sight mounting mechanism for tactical firearms having a cantilevered mount plate or section that permits removable assembly of an optical sighing device, such as an electronic reflex red-dot or colored indicator sight device in co-witnessing registry with the metal sighting system of the firearm.

It is also a feature of the present invention to provide a novel co-witnessing sight mounting mechanism for tactical firearms having a pivotally mounted sight base member that is interchangeable with a conventional leaf sight mechanism of an AK-47 type tactical firearm without any requirement for modification of the rear sight block of the firearm in any manner whatever.

Other and further objects and features of the present invention will become apparent to one skilled in the art upon a thorough review of the various apparatus and method that is discussed in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the preferred embodiment thereof which is illustrated in the appended drawings, which drawings are incorporated as a part hereof.

It is to be noted however, that the appended drawings illustrate only a typical embodiment of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

In the Drawings:

FIG. 1 is a side elevation view showing an intermediate portion and particularly the sight mount block of a typical AK-47 tactical rifle, and further showing a co-witnessing sight mount embodying the principles of the present invention being pivotally mounted to the sight mount block and providing support for an electronic reflex sighting device;

FIG. 2 is a side elevation view similar to FIG. 1, showing the co-witnessing rear sight mount pivoted forwardly to a position clear of the receiver cover of the firearm;

FIG. 3 is a top view showing the sight mount block portion of an AK-47 tactical rifle and showing the co-witnessing sight mount being pivoted to the position shown in FIG. 2;

FIG. 4 is an isometric illustration showing bottom, side and forward portions of the co-witnessing sight mount of the present invention and showing the downwardly facing magnet receptacles of the mount;

FIG. 5 is another isometric illustration showing the top and side of the co-witnessing sight mount base and further showing a metal leaf-spring sighting element positioned in assembly with the front portion thereof;

FIG. 6 a top plan view showing the sight mount of FIG. 5 and further showing a lock or keeper element in secure assembly therewith;

FIG. 7 is a side elevation view showing the co-witnessing sight mount with the metal lock or keeper element positioned in releasable assembly therewith;

FIG. 8 is a section view taken along line 8-8 of FIG. 6 showing the co-witnessing sight mount and lock or keeper sighting element in assembly in locking and sighting position;

FIG. 9 is an end elevational view taken along line 9-9 of FIG. 7;

FIG. 10 is an isometric illustration showing the lock or keeper member in detail; and

FIG. 11 is an exploded isometric illustration showing the bottom and a side of the co-witnessing sight mount with its lock or keeper element in securing position and showing the magnet devices being separated from the magnet receptacles in the bottom portion of the mount.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings and first to FIG. 1, a rather short rear sight block of the receiver of a conventional AK-47 tactical rifle is shown generally at 10 with a co-witnessing sight mount base, being shown generally at 11 and representing the preferred embodiment of the present invention. The sight mount base 11 is assembled with the rear sight block 10 in substitution for the conventional pivotally mounted rear sighting device with which these types of firearms are typically provided. It is important to note that the structure of the conventional rear sight block of the receiver of the firearm is not modified in any manner whatever to adapt it for receiving the co-witnessing sight mount base 11 of the present invention. The co-witnessing sight mount base 11 is simply substituted for and is interchangeable with the conventional pivotally mounted rear sighting device of the firearm. The rear sight block 10 is positioned about a rear portion of the barrel of the firearm and is secured in place by means of pins, rivets or both. A receiver cover 12 is positioned to cover the receiver and bolt carrier and extends rearwardly of the sight mount block 10. The forward extremity of the receiver cover 12 secured in place by a rearmost portion of the rear sight block. The receiver cover 12 is composed of stamped sheet metal and thus is unsuitable for receiving sight mounting screws, and thus typically limits the mounting of sighting devices to the short sight mount block 10.

The rear sight block 10 defines a pair of spaced, generally parallel and upstanding sight mount ribs 13, as shown in FIG. 3, each having upwardly projecting sight mount members 14 that define sight mount openings 15. The sight mount openings have a “figure 8” configuration to permit the laterally extending pivot pins of a conventional pivotal sight member to be installed and to establish pivotal movement within the sight mount openings 15. A leaf spring member 16 is spot welded or otherwise secured to the sight mount block 10 and is located between the sight mount ribs 13. The forward end of the leaf spring member 16 provides a spring force against the forward end of the conventional pivotal sighting member, ahead of the laterally extending pivot pins, thus urging the pivotal sight member to its seated or aiming position with respect to the sight mount block 10.

FIGS. 1-3 also show the co-witnessing sight mount base 11, being pivotally mounted in assembly with the sight mount block 10 of the firearm. The co-witnessing sight mount base 11 is merely substituted for the conventional pivotal sight device of a firearm, such as the AK 47 firearm mentioned above. These FIGS. further show an electronic reflex or red dot type sighting device 18 being mounted to the sight mount base 11 for establishing a co-witnessing relation with the rear sighting notch of a lock or keeper member 20 that is shown in FIGS. 5-8. This co-witnessing relation permits the user of the firearm to selectively use the electronically generated sighting dot or the rear sighting notch of the lock or keeper member 20 as will be explained in greater detail below. It should be borne in mind that the rear sighting notch may be defined by a sight projection that is integral with or mounted to the sight mount base 11 if desired. Thus, it is not intended to restrict the present invention to a sighting notch that is defined by the lock or keeper member that is shown in FIGS. 5-9 and described below.

FIGS. 4 and 5 are isometric illustrations also showing lower and upper portions of the co-witnessing sight mount base 11 and presenting its geometry in detail. The sight mount base 11 is maintained in pivotal assembly with the rear sight block of the AK-47 receiver by means of opposed, laterally projecting pivot members 21 and 22 that are preferably integral with a forward elongated portion 23 of the sight mount base 11. The pivot members 21 and 22 are received by the opposed pivot openings 15 of the rear sight block of the AK-47 firearm in the same manner as the pivot members of a conventional pivotal leaf sight are received.

As shown in FIGS. 4 and 5 the co-witnessing sight mount base 11 defines a mount body 24 having the elongate pivot connector section 23 projecting forwardly therefrom and supporting the opposed pivot members 21 and 22. The pivot members, as indicated above, are preferably integral with the elongate pivot connector section 23, though they can be defined by a pin member press-fitted within a transversely oriented bore or they can be secured to the pivot connector section 23 in any other manner. Since the co-witnessing sight mount base 11 is pivotally assembled to the rear sight block 20 of the AK-47 receiver, it is pivotally moveable between a sighting position, shown in FIG. 1 and an out of the way position shown in FIG. 2. The out of the way position clears the sight mount from its normal sighting position, immediately above the receiver cover 12, and permits the receiver cover to be removed for firearm servicing or repair, without any necessity for releasing the pivotal connection of the sight mount base 11 to the rear sight block 10 of the firearm.

It is desirable that the sight mount base 11 of the present invention be stabilized relative to the rear sight block 10 during aiming and firing of the firearm so that precision firearm use can be accomplished and effectively maintained even during conditions of rapid fire. To accomplish this feature, the sight mount base 11 is composed of a non-magnetic material, such as machined stainless steel or an aluminum alloy or titanium material and defines a pair of downwardly facing magnet receptacles 30 and 32 within which magnet devices 34 and 36 are located as shown in FIGS. 7, 8 and 11. The magnet devices may be press-fitted within the receptacles or may be secured within the receptacles in any other suitable manner. When the sight mount base 11 is located at its lowered or sighting position, the magnet devices will engage or be in close proximity to the ferrous metal structure of the rear sight block 10 and thus will continuously urge the sight mount base 11 toward the rear sight block, thus stabilizing it against movement from its sighting position. Should the recoil forces, during firing of the firearm, cause the sight mount base 11 to be moved or bounce slightly from the rear sight block, this movement will be very small, and the forces of the magnets will quickly return the sight mount to its original firing position. Even during rapid fire or automatic fire the forces of the magnets will overcome any sight bounce between rounds fired, so that each round fired will be accurately aimed.

A cantilevered sight mount plate 42 extends rearwardly from the mount body 26 and, when the co-witnessing sight mount base 11 is in aiming and firing position relative to the rear sight block of the firearm, the cantilevered mount plate 42 will be disposed in spaced relation or in touching relation with the thin sheet metal receiver cover 12, but will not be connected to or supported by the receiver cover. The cantilevered mount plate 42 is preferably formed integrally with the mount body 24, so that the co-witnessing sight mount base 11 can be provided in the form of a one piece member. Alternatively, however, the co-witnessing sight mount base 11 can be composed of interconnected structural components without departing from the spirit and scope of the present invention.

The cantilevered mount plate 42, which is shown in detail in FIGS. 4-9, defines an upper planar surface 44 and has a plurality of upstanding locator projections 46 for establishing precision location of an electronic reflex sighting device 18 or any other suitable sighting device on the cantilevered mount plate. Additionally, the cantilevered mount plate 42 is provided with drilled and tapped holes 47 so that a sighting device can be firmly but releasably secured thereto by means of mounting screws. The cantilevered mount plate 42 is also provided with generally parallel side flanges 48 and 50 to enhance the structural integrity of the mount plate and is also provided with drilled and tapped mounting holes 52 at each side to permit attachment of a sight protective shroud member 54, shown in FIG. 1, by mounting screws or by any other means for secure but removable shroud attachment. The upper generally planar surface 44 of the cantilevered mount plate is disposed in generally parallel relation with the generally planar upper surface 56 of the mount body and is laterally offset and lower than the surface 56. This feature positions the optical sighting device sufficiently low that the mechanical or iron sight is visible within or co-witnessed with the optical sighting device.

It is desirable to provide the co-witnessing sight mount base 11 with a metal sighting device that can be removed and replaced with a different metal sighting device if desired. To accomplish this feature, the forward elongated portion 23 and the body structure 24 of the sight mount base 11 defines a substantially planar surface 56, as shown in FIG. 5. A pair of retainer posts 58 and 60 project upwardly from the substantially planar surface 56 and are aligned with the center-line C/L of the sight mount base 11 as shown in FIG. 6. The retainer posts 58 and 60 are preferably integral components of the one piece sight mount base 12 and each define enlarged retainer heads that are of greater dimension as compared with the dimension of the retainer posts. If desired, the retainer posts may conveniently take the form of pin members, such as hardened pins, that are press-fitted or otherwise secured within pin receptacles of the sight mount. A retainer or keeper locking projection 62 also extends upwardly from the body structure 26 of the one piece sight mount base 12.

The lock or keeper member 20, which is shown in FIGS. 5-8 and is shown independently in FIG. 10 is an elongate member, preferably composed of a metal material, such as stamped metal. The lock or keeper member 20 is secured in position by the retainer pins 58 and 60 and serves, in concert with the magnet members 34 and 36, to secure the sight mount base 11 against pivotal movement from its sighting position. Additionally, the lock or keeper member 20 provides an upstanding rear end portion 61 having a rear sight notch 63, the upstanding rear end portion and its sight notch 63 being positioned in co-witnessing sighting relation with the electronic reflex sight device 18. The lock or keeper member 20 defines a pair of key-holes 64 and 66 having large openings 68 and 70 of greater dimension than the diameter of the locator posts 58 and 60 and the dimension of the heads of the locator posts so that the lock or keeper member 20 can be easily and efficiently assembled to the sight mount base 11 in the manner that is shown in FIGS. 5-8. The key-holes 64 and 66 are open to slots 72 and 74 that are each defined by spaced guide edges or surfaces 76 and 78. The spacing of the guide edges or surfaces 76 and 78 is only slightly greater than the diameter of the locator posts 58 and 60 so that the lock or keeper member 20 will be prevented from lateral movement relative to the locator posts and sight mount. After the large openings 68 and 70 of the key holes have been positioned over the heads of the locator pins, the lock or keeper member 20 is moved linearly and rearwardly. This rearward locking movement brings a retainer opening 80 of the lock or keeper member 20 into registry with the locking projection 62 so that the locking projection enters the retainer opening 80 and secures the lock or keeper member 20 in releasable retained assembly with the one-piece sight mount base 11. As the rear portion of the lock or keeper member 20 is moved over the locking projection 62 the rear portion of the lock or keeper member will be lifted slightly, causing slight bending of the lock or keeper member 20. Rearward movement of the lock or keeper member 20 also moves the lateral guide edges or surfaces 76 and 78 of each keyhole into contact with opposed sides of the locator posts 58 and 60 below the heads of the posts. This tight fitting relation of the lateral guide edges or surfaces 76 and 78 with the locator posts ensures against any lateral movement of the leaf-spring sight member relative to the one-piece sight mount base 11 so that accuracy of aiming is maintained.

To remove the lock or keeper member 20, the rear portion of the leaf-spring sight member will be manually lifted to disengage the locking projection 62 from the retainer opening 80, thus causing slight bending of the leaf-spring sight member. With this accomplished, sufficient manual force is applied to the leaf-spring sight member to move it forwardly until the large openings 64 and 66 are in registry with the locator posts 58 and 60. Then the leaf-spring sight member 14 can be separated from the one-piece sight mount base 11 and can be replaced with another lock or retainer member of a different character if desired.

Since the one-piece sight mount base 12 is pivotally mounted to the sight mount block of the receiver of firearms, such as the AK-47, it is desirable to prevent pivotal movement of the mount while the mount is located at its aiming position, such as shown in FIGS. 5-8. This feature is accomplished by providing the forward end portion of the lock or keeper member 20 with a downwardly and laterally extending offset end portion 86. This offset end portion is disposed in contact with an upwardly facing surface 87 of the sight mount block 10 of the firearm, forwardly of the pivot openings 15 shown in FIG. 1. The offset end portion 86 of the lock or keeper member 20 provides resistance to pivotal movement of the mount base 11 about its pivot pins during use of the firearm and yet is easily removed, without the necessity for special tools, with it is desired to pivot the mount to the out of the way position shown in FIGS. 1 and 3.

In view of the foregoing it is evident that the present invention is one well adapted to attain all of the objects and features hereinabove set forth, together with other objects and features which are inherent in the apparatus disclosed herein.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its spirit or essential characteristics. The present embodiment is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein. 

I claim:
 1. A sight mount for a firearm having a rear sight block defining opposed pivot openings and having a stamped metal receiver cover extending rearwardly of the rear sight block, said sight mount comprising: a mount base having opposed pivot pins received by opposed pivot openings of a rear sight block of a firearm and being pivotally moveable from a sighting position to an out of the way position clear of the stamped metal receiver cover, said mount base defining lock retainer members; a sight support platform projecting rearwardly from said mount base and providing support for an optical sighting device mounted thereto; a lock member having releasable locking engagement with said lock retainer members and having a portion there engaging the rear sight block and preventing pivotal movement of said mount base from said sighting position; and a rear sight member having a sighting notch and being visible in co-witnessing relation with the optical sighting device.
 2. The sight mount of claim 1, comprising: said mount base having an elongate forwardly extending portion having said opposed pivot pins projecting laterally therefrom; each of said lock retainer members projecting upwardly from said mount base and having a defined width; retainer heads of greater dimension as compared with said defined width defining the upper extremity of each of said lock retainer members; and said lock member having keyholes for each of said lock retainer members, said keyholes being defined by openings of greater dimension than the dimension of said retainer heads and slots of a dimension receiving said lock retainer members in close fitting relation, said lock member being linearly moveable relative to said lock retainer members for selective registry of said keyholes with said lock retainer members and retainer heads.
 3. The sight mount of claim 1, comprising: said lock member being composed of substantially planar strip material.
 4. The sight mount of claim 1, comprising: an upstanding rear end portion of said lock member defining said rear sight member and said sighting notch.
 5. The sight mount of claim 1, comprising: a forward end portion of said lock member being downwardly offset and being disposed in engagement with the sight mount block of the firearm forwardly of said pivot pin and preventing pivotal movement of said sight mount base.
 6. The sight mount of claim 1, comprising: a magnet receptacle being defined in said mount base and, with said mount base in said sighting position, facing the sight mount block of the firearm; and a magnet member being secured within said magnet receptacle and applying magnetic force to the sight mount block urging said sight mount base toward said sighting position.
 8. A sight mount for a firearm having a rear sight block defining opposed pivot openings and having a stamped metal receiver cover extending rearwardly of the rear sight block, said sight mount comprising: a mount base being secured to the rear sight block and having a sight support platform projecting rearwardly therefrom and providing support for an optical sighting device mounted thereto; lock retainer members projecting upwardly from said mount base; a lock member having releasable locking engagement with said lock retainer members and having a portion thereof engaging the rear sight block and securing said mount base against movement from said sighting position; and a rear sight member having a sighting notch and being visible in co-witnessing relation with the optical sighting device.
 9. The sight mount of claim 8, comprising: said mount base having pivotal connection with the sight mount block of the firearm; lock retainer members projecting upwardly from said mount base a lock member having releasable locking engagement with said lock retainer members and having a portion thereof engaging the rear sight block and securing said mount base against movement from said sighting position; and a rear sight member being defined by said lock member and having a sighting notch and being visible in co-witnessing relation with the optical sighting device.
 10. The sight mount of claim 8, comprising: said sight mount defining a first upper surface; and said sight support platform having a second upper surface being located in substantially parallel relation with said first upper surface and is laterally offset and below the level of said first upper surface.
 11. The sight mount of claim 8, comprising: lock retainer members projecting upwardly from said mount base and having a defined width; retainer heads of greater dimension as compared with said defined width defining the upper extremity of each of said lock retainer members; and said lock member having keyholes for each of said lock retainer members, said keyholes being defined by openings of greater dimension than the dimension of said retainer heads and slots of a dimension receiving said lock retainer members in close fitting relation, said lock member being linearly moveable relative to said lock retainer members for selective registry of said keyholes with said lock retainer members and retainer heads.
 12. The sight mount of claim 8, comprising: said lock retainer members each having a post section having a defined width and having a retainer head of greater dimension than said defined width; and said lock member having keyholes for each of said lock retainer members, said keyholes being defined by openings of greater dimension than the dimension of said retainer heads and having slots of a dimension receiving said post section of said lock retainer members in close fitting relation, said lock member being linearly moveable relative to said lock retainer members for selective registry of said keyholes with said lock retainer members and retainer heads.
 13. The sight mount of claim 4, comprising: an upstanding rear end portion of said lock member defining said rear sight member and said sighting notch.
 14. The sight mount of claim 8, comprising: a forward end portion of said lock member being downwardly offset and being disposed in engagement with the sight mount block of the firearm forwardly of said pivot pin and preventing pivotal movement of said sight mount base.
 15. The sight mount of claim 8, comprising: a magnet receptacle being defined in said mount base and, with said mount base in said sighting position, facing the sight mount block of the firearm; and a magnet member being secured within said magnet receptacle and applying magnetic force to the sight mount block urging said sight mount base toward said sighting position.
 16. A sight mount for a firearm having a rear sight block defining opposed pivot openings and having a stamped metal receiver cover extending rearwardly of the rear sight block, said sight mount comprising: a mount base defining an upper surface and having opposed pivot pins received by opposed pivot openings of a rear sight block of a firearm and being pivotally moveable from a sighting position to an out of the way position clear of the stamped metal receiver cover, said mount base defining lock retainer members; a sight support platform projecting rearwardly from said mount base and providing support for an optical sighting device mounted thereto; a lock member having releasable locking engagement with said lock retainer members and having a portion there engaging the rear sight block and preventing pivotal movement of said mount base from said sighting position; and a rear sight member having a sighting notch and being visible in co-witnessing relation with the optical sighting device; said sight support platform having an upper surface being lower than said upper surface and positioning an optical sighting device sufficiently low that said rear sight member is visible in co-witnessing relation through the optical sighting device.
 17. The sight mount of claim 1, comprising: said mount base having an elongate forwardly extending portion having said opposed pivot pins projecting laterally therefrom; each of said lock retainer members projecting upwardly from said mount base and having a defined width; retainer heads of greater dimension as compared with said defined width defining the upper extremity of each of said lock retainer members; and said lock member having keyholes for each of said lock retainer members, said keyholes being defined by openings of greater dimension than the dimension of said retainer heads and slots of a dimension receiving said lock retainer members in close fitting relation, said lock member being linearly moveable relative to said lock retainer members for selective registry of said keyholes with said lock retainer members and retainer heads.
 18. The sight mount of claim 8, comprising: a magnet receptacle being defined in said mount base and, with said mount base in said sighting position, facing the sight mount block of the firearm; and a magnet member being secured within said magnet receptacle and applying magnetic force to the sight mount block urging said sight mount base toward said sighting position. 